Autodetect processor architecture used for tests

[BCSharp]

Useful on macOS.

[slozier]

ProcessArchitecture doesn't look like an exact mapping for TargetPlatform, but I guess it sort of works.

Based on docs, if we omit the TargetPlatform tag it'll auto-detect. So might be slightly cleaner to not default platform to anything and omit RunConfiguration if unset?

[slozier]

Thanks!

[BCSharp]

Hmm, it seems not to work for netcoreapp3.1. I see it is EOL since 2 years. Do you intend to keep it around for longer?

UPDATE: I see that netcoreapp3.1 is simply not available for ARM64.

[slozier]

I'm fine with ditching netcoreapp3.1. Even net6.0 is already out of support. MS is moving a bit too fast for my taste. I was also considering dropping the netstandard2.0 target but maybe too early for that...

[BCSharp]

If you are planning to do a release soon, maybe it's worth waiting with the removal till right after the release.

[slozier]

Yes, I do want to release soon. .NET 9 issue has come up a number of times. Anyway, I just need to figure out the .NET tool issue and I can start testing the packages.